Package net.sf.saxon.expr.sort

Class DocumentOrderIterator

java.lang.Object

net.sf.saxon.expr.sort.DocumentOrderIterator

All Implemented Interfaces:

Closeable, AutoCloseable, Sortable, SequenceIterator<NodeInfo>

public final class DocumentOrderIterator
extends Object
implements SequenceIterator<NodeInfo>, Sortable

DocumentOrderIterator takes as input an iteration of nodes in any order, and returns as output an iteration of the same nodes in document order, eliminating any duplicates. An error occurs if the input sequence contains items that are not nodes.

Field Summary

Fields inherited from interface net.sf.saxon.om.SequenceIterator

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

Constructors

Constructor	Description
DocumentOrderIterator(SequenceIterator<?> base, ItemOrderComparer comparer)	Iterate over a sequence in document order.

Method Summary

Modifier and Type	Method	Description
void	close()	Close the iterator.
int	compare(int a, int b)	Compare two nodes in document sequence (needed to implement the Sortable interface)
int	getProperties()	Get properties of this iterator, as a bit-significant integer.
NodeInfo	next()	Get the next item in the sequence.
void	swap(int a, int b)	Swap two nodes (needed to implement the Sortable interface)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface net.sf.saxon.om.SequenceIterator

forEachOrFail, materialize

Constructor Detail

DocumentOrderIterator

public DocumentOrderIterator(SequenceIterator<?> base,
                             ItemOrderComparer comparer)
                      throws XPathException

Iterate over a sequence in document order.

Parameters:

base - the input sequence to be sorted

comparer - the comparer used for comparing node positions

Throws:

XPathException - if the input sequence cannot be evaluated, or if it contains an item that is not a node

Method Detail

compare

public int compare(int a,
                   int b)

Compare two nodes in document sequence (needed to implement the Sortable interface)

Specified by:

compare in interface Sortable

Returns:

<0 if obj[a]<obj[b], 0 if obj[a]=obj[b], >0 if obj[a]>obj[b]

swap

public void swap(int a,
                 int b)

Swap two nodes (needed to implement the Sortable interface)

Specified by:

swap in interface Sortable

next

public NodeInfo next()
              throws XPathException

Description copied from interface: SequenceIterator

Get the next item in the sequence. This method changes the state of the iterator.

Specified by:

next in interface SequenceIterator<NodeInfo>

Returns:

the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.

Throws:

XPathException - if an error occurs retrieving the next item

getProperties

public int getProperties()

Get properties of this iterator, as a bit-significant integer.

Specified by:

getProperties in interface SequenceIterator<NodeInfo>

Returns:

the properties of this iterator. This will be some combination of properties such as SequenceIterator.GROUNDED, SequenceIterator.LAST_POSITION_FINDER, and SequenceIterator.LOOKAHEAD. It is always acceptable to return the value zero, indicating that there are no known special properties. It is acceptable for the properties of the iterator to change depending on its state.

close

public void close()

Description copied from interface: SequenceIterator

Close the iterator. This indicates to the supplier of the data that the client does not require any more items to be delivered by the iterator. This may enable the supplier to release resources. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.

For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.

Closing an iterator is important when the data is being "pushed" in another thread. Closing the iterator terminates that thread and means that it needs to do no additional work. Indeed, failing to close the iterator may cause the push thread to hang waiting for the buffer to be emptied.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface SequenceIterator<NodeInfo>